Some predictions might be the tokens "I don't know", but that is based on the model mapping your text to those tokens by having seen many similar "I don't know" responses to such contexts, it didn't do any introspective logic to produce that "I don't know", and its possible it actually does know if it followed another branch there so "I don't know" is often not even true.
If they had an introspective part that stops the prediction when its too unreliable it would no longer just be token prediction engine, and I believe we need such a part for them to become what I call smart. I don't think LLM will ever stop being dumb without such an introspective part to them.
And no, that introspective part is not a part of the token predictor. At least not in us humans, the feeling of certainty we have is not a prediction, it is bundled with our thoughts, so we get both "answer is a bear" and "certainty is low", we don't get just one of those as a "prediction".
Will LLM become smart as humans with such an introspective part? I don't know, but I think they will never become as smart as humans without one.
Note: The certainty score has to be per conclusion or response, not per token. You can't evaluate a responses validity by aggregating the weight of each token. Meaning its a logic engine, not token engine, that evaluates the certainty of a statement being correct or not instead of a token being correct or not. That is the level human thinking works at and seems to be dramatically more efficient.